Different Effects of Mass and Damping on Performance of Vibration and Wind Energy Harvesters**This work was financially supported by the R&D project of State Grid Corporation of China under Grant 5700-202036164A-0-0-00

Piezoelectric energy harvesters which scavenge energy from ambient vibrations and winds attract increasing attention as the power sources of wireless sensor nodes. For these two types of harvesters, the optimal parameters are much different, but few references discussed this type of differences, which will be evaluated by deliberately designed experiments in this work. By taking the harvesters with the same piezoelectric composite beam configuration but different equivalent masses as examples, the differences were analyzed theoretically and experimentally. The equivalent masses are modified by changing the masses of the proof mass or the bluff body. In vibration energy harvesting, as we know, heavier mass is preferred for the lower resonant frequency and the higher electrical output. Decreasing the mechanical damping ratio is helpful to enlarge the output power at resonance but adversely narrows the frequency bandwidth. On the contrary, in wind energy harvesting, theoretical results show that smaller mechanical damping ratio is preferred and the experimental results show that lighter mass is preferred for the higher output power and the lower cut-in speed of galloping. The conclusions are valuable to developing efficient small- or micro-scale WEHs.